The present invention relates to a device for adjusting a relative angle of rotation of an internal combustion engine camshaft to a drive wheel and, more particularly, to a device in which a hydraulic linear motor is the actuating arrangement which acts upon an actuating mechanism between the drive wheel and the camshaft.
A device of this general type is known, for example, from EP-A-0 245 791 wherein the linear motor interacts with an adjusting mechanism which is used essentially in a front-face recess of the angularly adjustable shaft or camshaft. To this adjusting mechanism, which insignificantly influences the overall length of the internal-combustion engine, the linear hydraulic motor is assigned on a detachable engine power section cover with integrated hydraulic pipes and a control device for utilizing the space to the front-face end of the adjustable shaft or of the adjusting mechanism. The actuating of the linear hydraulic motor takes place by a hydraulic system which is separate from the internal combustion engine and has a separately driven pump.
In addition, a device has been suggested for adjusting the relative angle of rotation of a shaft to a drive wheel as seen in EP-A-0 363 600 in which a rotor of a hydraulic motor, which interacts with the adjusting mechanism of a first adjustable camshaft of an internal-combustion engine, is acted upon by the delivered flow of a hydraulic pump driven by a second camshaft. In this device, the hydraulic pump and the hydraulic motor, including the hydraulic pipes, form a unit which is assigned to the above-mentioned shafts and which is integrated in a power section area of the internal-combustion engine which is used for driving the shafts.
The present invention is based on the object of combining a device of the above-mentioned type with a hydraulic pump such that a compact space-saving unit is achieved for the structural integration in or on the internal combustion engine.
This object has been achieved in accordance with the present invention by such that a hydraulic pump with a pump rotor is arranged coaxially with respect to the longitudinal or adjustment axis of the linear motor.
The combination of the hydraulic pump, also known as a hydrostatic pump, and the linear motor in a coaxial arrangement advantageously results in a compact space-saving unit. This unit may, at the same time, serve as the smallest structural or assembly unit. For achieving a particularly compact space-saving unit, the linear motor and the hydraulic pump are arranged coaxially with respect to the shaft with the adjustable angle of rotation on a detachably constructed engine power section cover, in which case the unit according to the present invention and the engine power section cover form the next larger structural or assembly unit. In this arrangement, parts of the unit according to the present invention comprising the hydraulic pump and the linear motor may be an integral component of the engine power section cover. However, a separate construction of the unit according to the invention and of the engine power section cover is also conceivable.
The present invention can be implemented particularly advantageously by the selection of a radial piston pump and a linear motor constructed as a cylinder/piston unit. The radial piston pump, which is relatively small in size but has a sufficient delivered flow and a very high delivery pressure, therefore promotes the compact construction of the unit, in which the selected construction of the linear motor permits a good constructional adaptation to the selected radial piston pump. Consequently, an especially advantageous embodiment is achieved by the arrangement of the radial piston pump on the engine power section cover on the side of the shaft, in which the pump rotor is disposed in a rotatably movable manner on the periphery of the cylinder of the linear motor. For this extremely compactly configured unit, the drive of the radial piston pump can be achieved elegantly by simple devices by providing a radial piston pump which is acted upon on the inside and has a pump housing which is constructed in the engine power section cover, is open on the shaft side, and receives the pump rotor which is in a shaft-side driving connection by way of a plug-in arrangement. When the plug-in arrangement is in parallel to the mounting direction, the suggested plug-in arrangement considerably promotes the mounting of the structural or assembly unit according to the invention.
The unit combined according to the invention and comprising a pump rotor of the hydraulic pump or of the radial piston pump which is disposed on the cylinder of the linear motor in a rotatably movable manner results in special advantages with respect to its manufacture and the mounting of details. This results because a separate cylinder of the linear motor, which is constructed with different outside diameters, is arranged in a step bore of the engine power section cover, and the cylinder, on the shaft side, is equipped with flanged bushes for the slidable bearing of the pump rotor receiving radially displaceable delivery pistons, in which construction the flanged bushes comprise control openings on the intake side and the delivery side which are distributed on the periphery for the connection with the inflow and outflow chambers arranged in the cylinder wall.
The development of functional units of the hydraulic pump or of the radial piston pump in the wall of the cylinder of the linear motor results in additional simplification because the inflow chamber and the outflow chamber are each connected with an essentially axially directed duct which is arranged in the cylinder wall, in which this duct is connected by way of a circumferential groove in the periphery of the cylinder of the linear motor with a pipe arranged in the engine power section cover. If, in addition, the above-mentioned ducts are arranged from the shaft-side end of the cylinder in its cylinder wall, a flanged nut can be assigned to the cylinder on the shaft-side end for the tight sealing of the intake duct and of the delivery duct which also, with its outer edge area, is used for the axial securing of the flanged bush for the rotatably movable bearing of the pump rotor on the cylinder.
For radial piston pumps, which are acted upon on the inside and have a delivery piston which is radially movable in the pump rotor, the interaction of their radially outer ends with a sliding ring arranged in the pump housing is known. For a pump housing, which is constructed in the engine power section cover and is open on the shaft side, a separate fixing of the position of this slide ring is not required because, in a further development embodiment of the present invention, a generator wheel may be assigned with axial play to the pump housing which is open on the shaft side. In this embodiment, the generator wheel may be, for example, in a non-rotatable connection with the plug-in arrangement for the pump rotor. However, the generator wheel may also be constructed in one piece with the pump rotor, in which case the axial assignment of the pump rotor to the pump housing integrated in the engine power section cover may be implemented by the plug-in arrangement.
Further embodiments of the invention relate to the arrangement of the hydraulic pipes in the engine power section cover, in which configuration, for avoiding a separate hydraulic system, for example, the intake pipe in the engine power section cover is connected with the lubricant circulating system of the internal-combustion engine. For a continuous adjustment with a secure holding of the piston in any desirable position in the angle of rotation, the piston of the linear motor is constructed as a differential piston, in which pressure lines, which are provided so that this differential piston is acted upon on both sides, are controlled by a timing valve, in which case hydraulic liquid gradually shut off by the timing valve, by way of a discharge pipe in the engine power section cover which leads out on the side of the engine, is returned to the lubricant circulating system of the internal combustion engine. In addition, the outer dimensions of a hydraulic pump can be desirably reduced by the combination with an accumulator, in which configuration the accumulator is preferably integrated on the engine power section cover for avoiding separate pipes.
Furthermore, in order not to disadvantageously influence the dimensioning of important parts in the overall arrangement for the purpose of an acceptable mounting process, the structural or assembly unit according to the present invention further comprises a coupling element of the adjusting system which is connected by a coupling rod and acts in an angle adjusting manner between the shaft and the drive wheel. Thus, a significant function unit of the overall device can be constructed separately from the internal-combustion engine and can be introduced into the assembly line of the internal-combustion engine.
It remains within the scope of the present invention to arrange the hydraulic pump also on the shaft which can be adjusted with respect to its angle of rotation, and to hold the pump housing to be non-rotatable on the cover side by way of a plug-in arrangement. It is also conceivable to arrange the linear pump, the hydraulic pump, possibly with the generator wheel, and the control device formed of lines and the timing valve in a separate part and to connect this part with the engine power section cover. This development also permits the separate manufacture of a function unit of the overall device. This development may be used for a low-cost retrofitting.